[PATCH] D83284: [InstCombine] Improve select -> phi canonicalization: consider more blocks

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp:2518
+    if (auto *PN = foldSelectToPhiImpl(Sel, I->getParent(), DT, Builder))
+      return PN;
+
----------------
It seems quite likely that some of the parents (or all of them) are going to be the same. Might it make sense to deduplicate?

```
// Collect likely candidates for placing the phi node.
SmallPtrSet<BasicBlock *, 4> CandidateBlocks;
CandidateBlocks.insert(Sel.getParent();
for (Value *V : Sel.operands())
  if (auto *I = dyn_cast<Instruction>(V))
    CandidateBlocks.insert(I->getParent());

for (BasicBlock *BB : CandidateBlocks)
  if (auto *PN = foldSelectToPhiImpl(Sel, BB, DT, Builder))
    return PN;
```


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D83284/new/

https://reviews.llvm.org/D83284